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Recent studies of the electric field effect on several bands of the laser induced phosphorescence excitation spectrum of 2, 4, 5-trimethylbenzaldehyde, isolated in a durene single crystal, revealed that the dipole moment associated with the most intense feature in the spectrum was the same, within experimental uncertainty, as that for the $T1(n\pi \ast )$ phosphorescence $origin1$. This result seems to indicate that either the assignment of this feature to the $T2(n\pi \ast )$ state is incorrect or that the $T2(n\pi \ast )$ state is strongly coupled to a set of $T1(n\pi \ast )$ vibronic levels. In order to determine the origin and generality of this result, we have mesured the electric field effect on the phosphorescence excitation spectra of 2, 4 and 2, 5-dimethylbenzaldehyde. The results of these experiments will be presented and compared with those for trimethylbenzaldehyde.